For example, Div. 4 and Div. 3 can merge into Div. 7, all problems are *800.

Div. 2 should be harder, for example, A is *2800, and B is *3500.

Div. 1 must be full of *3400 and *3500.

Also, the rating range will be:

Div. 7: $$$\le 2600$$$.

Div. 2: $$$2400 \sim 3200$$$.

Div. 1: $$$\ge 3000$$$.